RESPONSE OF SWISS CHARD (Beta vulgaris L. var. cicla L.) TO NITROGEN FERTILIZATION

Swiss chard may be cultivated for a single or in small scale of production for multiple harvest. The objective of the field experiment conducted in 2012-2014 was to determine the response of this vegetable crop to nitrogen fertilization. Lukullus and Green Silver cultivars were grown from direct seed sowing into the field and supplied with 100 or 200 kg N.ha(-1) by using ammonium nitrate and Entec 26. Harvest of leaves started at the end of June was made weekly till half of September, each time the yield of leaf blades and petioles were evaluated. At the end of July the samples were collected for chemical analysis. Results of the study proved that both tested N fertilizers were equally valuable sources of this nutrient for Swiss chard and the increase of its dose from 100 to 200 kg.ha(-1) was ineffective for crop yield, while caused the significant enhancement of nitrates accumulation. Leaf blades appeared to be a rich source of vitamin C and contained lower level of sugars and Ca while higher amounts of P and Mg if compared to petioles. Nitrates accumulation in leaf petioles was generally twice as high as in the blades. Green Silver cultivar produced higher yield of leaf petioles and higher amounts of chlorophyll showing smaller tendency for nitrates accumulation than Lukullus.